President Trump's attorney, Rudy Giuliani, took aim at special counsel Robert Mueller in an interview airing Sunday, criticizing what he called "unethical" tactics by prosecutors in Mueller's office after former Trump lawyer Michael Cohen pleaded guilty to lying to Congress.

In an interview with AM 970 in New York, Giuliani accused Mueller of crossing a line by "intimidating" Trump's allies into saying "what he believes [is] his version of the truth."

"They obviously exerted a lot of pressure on him. Mr. Cohen unfortunately has a history of significant lies in the past," Giuliani told host John Catsimatidis, reacting to Cohen's admission last Thursday that he lied to Congress when he previously detailed to the body the extent of the president's business dealings in Russia.

"This isn't a search for the truth. It's a witch hunt," Giuliani continued. "This is what is wrong with these special prosecutors and independent counsels. They think they are God."

"They seem to want to prosecute people at any cost, including the cost of ethical behavior and the rights of people."

The former New York City mayor, who joined Trump's legal team earlier this year to handle the White House's response to the special counsel probe, added that Mueller's prosecution of Paul Manafort, Trump's former campaign chairman, was intended to force Manafort to implicate Trump in collusion with Russia that Giuliani says never occurred.

"They want [Manafort] to give certain forms of evidence that would implicate the president in things that Mr. Manafort says are untrue," Giuliani said.

"And they are pressuring him, and creating a real risk that the man might commit perjury," he added. "This kind of pressure can create the risk of tainted testimony."

Mueller's office told a judge last Friday that prosecutors are considering further charges for the former Trump aide, who was accused earlier in the week of violating his plea agreement by lying to investigators.

Manafort "committed federal crimes by lying to the Federal Bureau of Investigation and the Special Counsel's Office on a variety of subject matters," Mueller wrote in court filings.

A judge has given Mueller's team until Dec. 7 to explain how Manafort allegedly violated his plea agreement. He is currently scheduled to be sentenced in March.